Evaluation and Comparison of Continuous Fine Particulate Matter Monitors for Measurement of Ambient Aerosols

Abstract

To provide a scientific basis for the selection and use of continuous monitors for exposure and/or health effects studies, and for compliance and episode measurements at strategic locations in the State of New Jersey, we evaluated the performance of seven continuous fine particulate matter (PM_2.5) monitors in the present study. Gravimetric samplers, as reference methods, were collocated with real-time instruments in both laboratory and field tests. The results of intercomparison of real-time monitors showed that the two nephelometers used in this study correlated extremely well (r^{2 ∼}0.97), and two tapered element oscillating monitors (TEOM 1400 and TEOM filter dynamics measurement system [FDMS]) correlated well (r²> 0.85), whereas two beta gauges displayed a weaker correlation (r² < 0.6). During a summertime controlled (laboratory) evaluation, the measurements made with the gravimetric method correlated well with the 24-hr integrated measurements made with the real-time monitors. The SidePak nephelometer overestimated the particle concentration by a factor of approximately 3.4 compared with the gravi-metric method. During a summertime field evaluation, the TEOM FDMS monitor reported approximately 30% higher mass concentration than the Federal Reference Method (FRM); and the difference could be explained by the loss of semi-volatile materials from the FRM sampler. Results also demonstrated that 24-hr average PM_2.5 mass concentrations measured by beta gauges and TEOM (50 °C) in winter correlated well with the integrated gravi-metric method. Seasonal differences were observed in the performance of the TEOM (50 °C) monitor in measuring the particle mass attributed to the higher semi-volatile material loss in the winter weather. In applying the real-time particulate matter monitoring data into Air Quality Index (AQI) reporting, the Conroy method and the 8-hr end-hour average method were both found to be suitable.